(G-255) Effect of Iron Oxide Infused Coaxially Electrospun Polydimethylsiloxane (PDMS) Fibers Under Magnetic Field for Aligned Nanofibers

Introduction:: Electrospinning is an electric-force-driven fiber production method that uses electrification upon liquid polymer droplets to force their elongation into nano/microfibers [1]. In an application of biomedical engineering, electrospun nano/microfiber mats are often used for in vitro cell culture and provide enhanced mechanical properties [2], e.g., guiding cell orientation, migration, etc. To create aligned electrospun microfibers, gap-collecting, magnetic field-aided collection, or centrifugal electrospinning methods can be used [3]. In this abstract, we propose to create an aligned nanofiber mat using iron oxide (Fe₂O₃)-infused polydimethylsiloxane (PDMS) nanofiber with a magnetic field. Given the high density (960 kg/m³) and curing rate, PDMS was selected to be coaxially electrospun alongside polyvinylpyrrolidone (PVP) (a water-soluble polymer that could be washed off the resulting mat). Combining Fe₂O₃-infused PDMS nanofiber and magnetic field application is expected to manipulate and control the nanofiber alignments during collection.


Materials and Methods:: A PDMS solution was prepared by mixing PDMS parts A and B in a 10:1 ratio (Sylgard 184) with 0.25 mL of tetrahydrofuran (THF; Sigma) to slow down the curing process during electrospinning. Then, different concentrations of Fe₂O₃ were added to the PDMS pre-gel solution. PVP (4 g; Sigma) was mixed with 6.4 mL of dimethylformamide (DMF; Sigma) until the PVP powder was completely dissolved into a thick and cloudy liquid. The PDMS solution was then fed into the inner (0.17 mm) needle, and the PVP solution was fed into the outer (1.07 mm) needle of the coaxial setup (Fig. 1(b)). Each needle was connected to two separate microfluidic pumps at constant rates of 0.5 mL/h and 1.25 mL/h for PDMS and PVP, respectively. The tip of the coaxial needle (22-17 gauge) was placed 7 cm over the collecting plates. We employed a gap collection using two collecting plates placed 0.5 cm away from each other. A constant voltage of 16.5 kV was applied to the tip of the coaxial needle and the collecting plates were grounded. Two magnets were used at various locations: fixed to the horizontal position at 15 cm away from the collectors and 0 – 3.5 cm away vertically from the collector. After finding the most effective position of magnets for alignment, different concentrations of Fe₂O_3­ in the PDMS were used to determine the effect on nanofiber alignment.


Results, Conclusions, and Discussions:: Various magnet positions and Fe₂O₃ concentrations exhibited different fiber alignments. We first investigated the effect of the magnetic field (Fig. 1(c)). The control (no magnetic field application) showed the average angle with respect to the x-axis was 27.5°, while the magnetic field due to two magnets positioned at 3.5 cm from the top of the collector improved significantly with an average angle of 13.0°. However, the alignment deteriorated when the magnets were placed on top of the collector (37.9°). Given that the 3.5 cm height presented the most alignment, we attempted further improvement by infusing Fe₂O₃ nanoparticles in the PDMS (Fig. 1(d)). Three different concentrations were investigated: 1, 5, and 10 % w/v. We observed that adding Fe₂O₃ indeed responds to the magnetic field. With 1% w/v Fe₂O₃, the alignment was slightly worse than without Fe₂O₃ infusion (23.7°). As the concentration increased, the alignments improved: 19.9° for the 5% w/v and 12.2° for the 10% w/v. Notably, the 10% w/v sample showed exceptional results with a variance of 4.78° and the highest clustering.
Manipulating electric fields in electrospinning with a magnet can affect the nanofiber orientation. Infusing a high concentration of Fe₂O₃ into the nanofiber could further improve the overall results with low variance, resulting in densely packed aligned nanofibers. Such a technique can be applied to the exploration of flexible biomedical platforms that require low flexural rigidities and high tolerance against mechanical bending can be expanded upon. The aligned microfiber mats could also create functional fibrous connective tissue (tendons).



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[1] N. Bhardwaj and S. C. Kundu. (2010). Electrospinning: A fascinating fiber fabrication technique. Biotechnology Advances, vol. 28, no. 3, pp. 325–347, 2010.




[2] S. Agarwal, J. H. Wendorff, and A. Greiner. (2008). Use of electrospinning technique for biomedical applications. Polymer, vol. 49, no. 26, pp. 5603–5621, 2008.




[3] A. J. Robinson, A. Pérez-Nava, S. C. Ali, J. B. Gonzáles-Campos, J. L. Holloway, E. M. Cosgriff-Hernandez. (2021). Comparative Analysis of Fiber Alignment Methods in Electrospinning. Matter. 2021 Mar 3;4(3):821-844.